Goldbeater&#39;s foil



Patented Nov. 16, 1943 GOLDBEATERS FOIL Donald D}. Swift, Hartford, 001111., assignor to M.

Swift & Sons, Inc, a corporation of Gon-nectiout No Drawing.

Application =Octob'er 28, 1939, Serial No. 301,796

3 Claims. (01. 29-11) 1 I Mypresent 'inventi on nel'ate's to the goldbeaters art and more particularly to an improved goldbea't'er s foil.

When gold or other precious base metal is beaten into metallic sheets, it is first rolled into a ribbon, the usual thickness of the ribbon being about 4 of an inch. This ribbon is cut into squares approximately 1 inches in width and the squares are filmed between membranes known as cutch paper, the trade name for a special paper made from ground animal hide. After the squares have been filmed between these papers, the resulting packet is beaten until the initial squares have spread to the full size of the cutch paper, about four inches in width. These expanded squares of metal are removed from the paper squares and are quartered, and the quartered squares are in turn filmed between membranes known as the goldbeaters skin to provide a packet form which is again beaten, each square now spreading to a diameter of about inches. These squares are again quartered and the process is repeated until the quartered squares become approximately six inches in diameter, the shape being somewhat irregular. These squares are preferably againquartered, filmed and beaten. Specially prepared membranes of animal origin are used for this purpose, these membranes being very expensive, and having certain recognized disadvantages in use, the principal disadvantage resulting from an unavoidable retention of fat content in the course of their preparation; the fat content makes their direct use for thin (shoder or mold) beating inadvisable, and they are therefore first used for thick (cutch) beating before they can be effectively used for thin beating. Furthermore, goldbeaters skin is not smooth, is not of uniform thickness, stretches about 3 or 4% under beating, is not uniformly tough in all directions, tends to split, and is hygroscopic, wherefore the quality of the beaten and I have found that the plasticizer, if present in excess quantity, tends to adversely affect the lubricant used with the goldbeaters skin during the beating operation. Inasmuch as a plasticizer is essential, I have discovered that a plasticizer such as tricresyl phosphate when used with the commercial cellulose acetate in quantities of between 8 to 10% gives the most satisfactory results. Other plasticizers or a plurality of plasticizers may also be found suitable; however, I prefer to keep the total percentage of plasticizer below 10%.

These foils, if desired, may be brushed or otherwise provided with any of the lubricating or gut preparations commonly employed as coatings for goldbeaters skin, consisting essentially of isinglass, gum arable, shellac, and spices such as saffron, cinnamon, and cloves in red wine. However, the cellulose acetate foil may be used to advantage without such a coating. For example, I have found that aluminum foils may be beaten with cellulose acetate foils without the use of any lubricating or "doctoring material. On the other hand, for best results, -I have found that a'lubricant is preferable for goldbeating. A preferred lubricant is disclosed in my copending application entitled Goldbeaters lubricant, filed October 28, 1939, Serial No. 301,797.

I have found that the use of the cellulose acetate as the goldbeaters skin wil reduce the beating time of the gold approximately as compared with the use of standard goldbeaters skin. Furthermore, beating with cellulose acetate foils gives the gold a very flat surface and a high initial burnishing. Inasmuch as the cellulose acetate with the 8 to 10% plasticizer will retain its elasticity under beating it can be immediately used for thin beating as it does not give or stretch. The gold will have a substantially flat and uniform thickness. The cellulose acetate foils can be obtained in a more uniform thickness than goldbeaters skin, will not stretch under use, and is non-splitting and uniformly tough in all directions.

Furthermore, the cellulose acetate is extremely cheap, is devoid of fat so that the foils can immediately be employed for mold beating, and is non-hygroscopic.

The durability of these new foils, that is their resistance to hammer blows, is superior to that of goldbeaters skin, and far superior to other substitutes that have been utilized such as Cellophane and the like. For example, I have found that Cellophane is hygroscopic in character and will crack if dehydrated. Therefore, the applica tion of a lubricant on Cellophane causes moisture in the Cellophane to affect the lubricant, or vice versa, and thus give indeterminate results. cellulose acetate with approximately 8% plasticizer will retain its elasticity under constant beating,-Ce11ophane and heavily plasticized cellulose acetate does not do so. Cellulose acetate also provides a bettersurface finish thanCellophane because of inherent surface conditions imposed during the process of manufacture, the cellulose acetate being made on highly polished rolls.

Although cellulose acetate has been found preferable for the above described use, due to its While I from .008 to .030 inch.

physical characteristics and its'low cost, other chemical compositions of similar physical nature may also be used, examples being ethyl cellulose, cellulose nitrates, styrene resins, methyl methacrylate resins, vinol chloride acetates, and phthalates such as propyl and methyl. The amount of plasticizer or softener used should be calculated or determined to :obtain a predetermined plasticity which will not permit the foil to permanently stretch under the hammer beating and produce a bulged center.

While I have described a specific material for 2. A metal beating packet comprising layers of material adapted to receive metal foils therebetween, said material comprising cellulose acetate and tricresyl phosphate plasticizer, the thickness of the layers being from .008 to .030 inch.

'3. A metal beating. packet comprising layers of material adapted to receive metal foils therebetween, said material comprising cellulose acetate and tricresyl phosphate plasticizer, the percentage of plasticizer being below 10 per cent, the thickness of the layers being from .008 to .030 inch.

DONALD D. SWIFT. 

